Transmission synchronizer



vs. o. wHrrE TRANSMISSION SYNCHRONIZER Re'. l22,265

Feb. 9, 1943.

original Filed Aug; 25. 19:57 2 sheets-sheet 2 Ressued Feb. 9, 1943 TRANSMIS SION SYNCHRONIZER Samuel 0. White, Muncie, Ind., assignor to Borg- Warner Corporation, Chicago, Ill., a corporation of Illinois Original No. 2,179,568, dated November 14, 1939, Serial No. 193,867, March 4, 1938, which is a division of Serial No. 160,844, August 25, 1937, now Patent No. 2,221,893, dated November 19, 1940. Application for reissue AJanuary 31, 1941,

Serial No. 376,902-

17 Claims.

This application is a division of my co-pending application Serial No. 160,844, filed August 25, 1937, and issued as Patent No. 2,221,893 on Nov. 19, 1940, entitled Transmission synchronizer.

This invention relates to improvements -in transmission synchronizers such ias those employed in the change-speed transmissions of motor vehicles to bring driving and driven power transmitting elements to the same speed before drivingly interlocking the elements through positive clutch means. The invention is particularly directed to transmission synchronizers of the socalled blocker type having means to prevent engagement of the positive drive clutch prior to the time that synchronization takes place.

An object of my invention is to provide an improved transmission synchronizer, of the blocker type, which requires a minimum of manual effort to effect blocking of the shiftable positive drive clutch member and to initiate operation of the synchronizing clutch.

Another object is to provide an improved transmission synchronizer as described, which has but relatively few parts and which may be installed in a change gear transmission in the same space heretofore occupied by a transmission synchronizer not of the blocker type.

A further object of the invention is to provide a transmission wherein the shiftable jaw clutch element is mounted upon a hub that is separate from the driven shaft but fixed thereon against axial movement. Whereas in prior synchronizers it has been customary to transmit shifting movement from the movable jaw clutch sleeve to a synchronizer element through the hub, which was mounted upon the driven shaft so as to be axially movable thereon, the present invention contemplates the provision of a direct frictional connection between the shiitable jaw clutch element and the synchronizer ele-ments, and to this end, employs a series of thrust members, operatively interposed between the shiftable jaw clutch element and the synchronizer element, and having a frictional thrust receiving engagement with the movable jaw clutch element.

A further object is to provide an improved transmission synchronizer as described, which requires but a minimum manual force to effect driving interengagement between the driving and driven element of the transmission once synchronization has been brought about.

An object of the invention is to provide an improved transmission synchronizer of this type, in which the parts are so constructed and arranged that the movement of the shifter element may be substantially smooth and continuous. In the past it has been universally considered necessary by manufacturers of automobiles and by manufacturers of .transmission gearing, to employ, between the movable clutch element and the thrust element of a synchronizing mechanism, a detent or poppet connection having a breakaway action for the purpose of transmitting movement from said movable clutch element to said thrust member for exerting axial pressure against the blocker-synchronizer rings of the mechanism. In such mechanisms, after having effected synchronization by initial movement of the shifter member in the direction of the gear position that has been selected, it is necessary to increase the force exerted against the shifter member in order to effect the break-away release of the movable clutch' member from the thrust element and allow the movable clutch element to advance through the blocker lteeth of the blockersynchronizer ring into clutching engagement with the clutch teeth of the gear that has been selected. The increased resistance to the movement of the shifter member, occasioned by this breaking-away of the detent connection, results in a denitely varying resistance in the progress of shifting. l

It is undoubtedly true that the shifting mechanism of modern automobiles operates more smoothly and requires less eiort than those of earlier mechanisms, and the varying resistance above noted may not be particularly prominent or serious in the case of a new transmission. However, as the parts become worn, these conditions are accentuated and in time may become decidedly noticeable, thus to destroy the desired drivers impression of a smooth continuous shift.

An object of the present invention is therefore to provide a transmission of-the type embodying a conventional form of synchroniser mechanism, in which the transmission of thrust from the movable clutch element to the thrust member, and theA movement of the movable clutch element from neutral position to gear engaged position, is accomplished without variation in the resistance to the movement of the shifter element other than the normal retarding of movement by the positive jaw blocker, and in which the wearing of the parts does not increase or create any variation in such resistance. To this end, the invention provides a. construction in which movement is transferred from the movable clutch element to the thrustr member solely through the medium o f apurelyfrictional engagement .having a constant coeiicient of resistance at all times in the shif ing operation, and the invention involves the discovery that synchronization can be accomplished Without the use of detent mechanisms which have hereto-fore been considered necessary.

Other objects, the advantages and uses of' the invention will become apparent after reading the following specification and claims, and after consideration of the drawings forming apart of this specification, wherein: l y l Fig. l is a fragmentary elevation, partially in section, of a change speed transmission mechanism incorporating one form of my improved synchronizer; y y

Fig. 2 is a sectional view' of `the same taken on the line 2 2 of Fig. l;

Fig. 3 is a sectional View of the same taken on the line 3-3 of Fig. l;

Fig. 4 is a perspective view of the thrust member embodied in the form shown in Fig. 1;

Fig. 5 a fragmentary sectional view illustrating a modication of the invention;

Fig. 6 is a plan view, partly in section, of a portion of the mechanism shown in Fig. 5;

Fig. 7 is an end elevation ofthe mechanism shown in Fig. 6;'and

Fig. 8 is a perspective yview of the thrust member of the form shown in Fig. 5.

I have selected for illustration herein, embodiments of my invention as applied to certain of the torque-transmitting members of a conventional change-speed transmission of the type used in motor vehicles and such as illustrated in my prior United States Patent No. 1,872,566.

With reference to Figs. l to 3l hereof, such transmission may include a drive shaft 2 having formed thereon an external gear 3 engageable with a gear #i carried on the transmission countershaft 5. A second gear 6 also carried on the countershaft 5 may mesh with the external teeth 'I of the transmission second speed gear 8, the gear Il being rotatably mounted upon the transmission driven shaft 9 but xed against axial movement relative thereto. The shafts 2 and 9 being coaxial, one end II of the shaft 9 may be piloted in the adjacent end of the shaft 2, as shown.

A clutch supporting member I2 is mounted upon the shaft 9 between the gear 3 and gear 8 and is keyed thereto, as indicated at I3. The member I2 is also fixed against axial movement relative to the shaft 9 by thrust washers I0 and serves as a support for the movable element I4 of a positive jaw clutch. Except rfor practical difficulties of construction, the member I2 could be formed integral with the shaft 9. The movable jawclutch element I4 may take the form of a sleeve having internal gear-like clutch teeth I5 slidably engaged with a complementary externally toothed portion I5 of the member I2 (see Fig. 2). A shift fork I'I received in an annular groove Ill formed in the outer wall of the clutch element I4 serves as a meansaxially to shift the member I4 selectively in the direction of the gear 3 or gear 8 as desired. Positive jaw clutch teeth conforming in` contour with the teeth IG upon the member I2 and in end to end register therewith are formed upon each of the gears 3 and 3, as illustrated at 2l and 22 respectively. Movement, therefore, of the clutch element I4 to the left, as viewed in Fig. 1, will serve positively to drivingly interconnect the drive member 2 with the shaft 9, and, in likel manner, movement of the clutchelement I4 to the right, will provide a direct drive connection between the gear 3 and the shaft 9. Such engagement of movable jaw clutch element I4 turning with the shaft 9, and the relatively fixed parts 2I or 22, as desired, I provide a friction clutch synchro- .nizer mechanism between the support member I2 and the gears 3 and 8. Such mechanism, in the construction illustrated, may comprise a pair of yforged bronze rings 24 and 25, respectively, one

located at each side of the support member I2 and each having a conical friction surface` 26 en- .gageable with a complementary friction surface 21 formed on an adjacent portion of the gear 3 and gear 8, respectively.

The synchronizer rings 24 and 25 may be drivingly connected to the support I2 as by means of integral lugs 29 formed on that side of each ring facing the support I2, the lugs extending into openings 3l located transversely through the member I2. The openings 3I may be of such diameter relative to the width of the lugs 29 as to permit a limited relative rotation between each ring and the member I2 an amount equal to, but not greater than, the width of the teeth formed on the movable positive clutch element I4. Except for the lugs 29 which limit relative rotation of the synchronizer ring, withrespect to the member I2 and its supporting rshaft 9, each of the rings is free to float between the member I2 and the adjacent friction clutch surfaces 26 of the gears 3 and 8 respectively. y

The rings 24 and. 25 each possess, in addition to the function of a friction clutch synchronizer element, the function of a blocker mechanism for preventing engagement of the jaws of the positive clutch I4-2I and I4-22, prior to the time that synchronism of the positive jaw clutch parts takes place. YThis function of the rings 24 and 25 may be carried out by the provision of radially extending external blocker teeth 33 and 34 formed on kthe outer peripheries of the rings 24 and 25, respectively, and conforming in contour to the clutch teeth 2| and 22 on the gears 3 and 8 respectively. The blocker teeth 33 and 34 may be further formed with those ends thereof acing the slidable clutch member I4 chamfered as indicated at 35 (see Fig. 3). The adjacent ends of the teeth I5 upon the clutch element I4 may likewise be chamfered as indicated at 36, so that movement of the jaw member I4 in the direction of the relatively fixed jaw teeth 2| and 22 may cause the registering chamfered surfaces 35 and 3E of the blocker teeth and jaw teeth I5 to contact along surfaces disposed angularly with respect to the axis of rotation of the clutch parts at such times as when the teeth 33 or 34 are not in direct end-to-end register with the teeth I6 upon the clutch support member I2. This condition of the partsmay exist whenever one of the two torque-transmitting members to be interconnected, such as the shaft 9 to the gear 3, or gear 8, is rotating at a speed dierent from the speed of the remaining member, hence causingthe synchroniser-blocker ring to be moved toward one or the other of its limits of rotation relative to the support I 2. As the parts approach synchronism, there Will be a relative reversal of rotation, thus causing the blocker teeth for a moment to register directly with the teeth I6 on the support I2, which position is indicated in full `will be no further obstruction of the movable .clutch element, and the latter may then move onlines of Fig. 3, and atA such moment, the clutch element I4 will be free to continue in its movement into engagement with the relatively fixed jaw clutch teeth toward which it has been initially moved. This blocking function of the synchronizer-blocker rings will, of course, take place only when the rings are urged toward their adjacent friction clutch complement so as to bring about frictional driving engagement between the synchronizer-blocker ring and the torque memberv with which the ring is engaged frictionally.

Means for causing the synchronizer-blocker ring to move first to block positive jaw clutch engagement and thereafter to synchronize the parts to be coupled, upon movement of the positive clutch element I4, may comprise a plurality of relatively light-weight and low inertia thrust members 4I, spaced at equal distances apart from one another about the circumference of v blocker teeth 33 and 34, respectively, are disposed.

vthe support member I2 and disposed parallel to,

Each of the thrust members 4I is formed of nat strip spring metal arched to form fiat central regions 44 friotionally engaged against flat interior friction surfaces 45 of the movable clutch member I4, and curved end regions 4B terminating in rolled bearing members 4'I in engagement with the peripheral surfaces 48 of the synchronizer rings 24 and 25 and adapted to engage the radial shoulder portions 23 at the commencement of a shifting operation.

The thrust members 4 I, in their original shape, are arched to a greater extent than that shown in Fig. 1 so that when installed they will be biased under compression, whereby to cause the flat central regions 44 to resiliently engage the friction faces 45.

. Movement ofthe shifter fork I1 in either direction to institute a shifting operation, will be transmitted through the movable clutch element I4.and the friction face 45 thereof to the thrust member 4I, solely as a result of the frictional engagement of the flat central region 44 thereof with the said friction face 45. This will cause the thrust members 4I to bear against and to urge one of the synchronizer blocker rings 24 or 25 toward its friction clutch complement, depending upon in which direction the positive clutch member I4 is urged. This initial axial movement of the synchronizer blocker ring will cause the ring, when engaged with its friction clutch complement, to turn with the part to which it is frictionally engaged, and will cause a relative rotation between the ring and the support member I2 in the direction of the movement of the part which is rotating at a superior speed, thus to cause the chamfered surfaces and 36 of the blocker teeth and the positive jaw clutch teeth I5 to move into blocking position, as indicated in dotted lines in Fig. 3. When the parts to be drivingly interlocked to the positive jaw clutch arrive at a synchronous speed relative the-reto, there will be a relative reversal of move- 4ment causing the blocker synchronizer ring to move toward the position indicated in full lines in Fig. 3. When such position is assumed, there wardly under the urging pressure of the shifter fork I1 until it arrives in positive clutch engagement with the teeth 2l or 22. During this latter stage of movement of the movable clutch element I4, it will move away from the thrust elements 4I, leaving the latter confined between the synchronizer blocker rings 24, 25, the friction surfaces 44, 45 continuing to offer the same uniform resistance to such movement, without variation. It would of course be possible for the resistance to the movement of the movable clutch element I4 to be greatly increased during the interval whe-n the clutch element is blocked by the blocker teeth, should the operator increase the pressure against the shifter fork. But such increased pressure is not necessary, and if shifting is performed properly by exerting a steady unvarying pressure against the shifter fork, the operation will progress with perfect smoothness and Without any variation in resistance in the mechanism. It is necessary, of course, in any event to wait until synchronization is complete before attempting to complete the shifting operation.

In the modification of the invention shown in Figs. 5 to 8 inclusive, the thrust members 4Ia may be of sheet metal, and may be urged outwardly into engagement with friction surfaces 45 by means of coil springs 50 engaged between the inner faces of the thrust members 4Ia and the peripheral faces 48a of the synchronizer blocker rings 24, 25. The thrust members 4Ia may be provided with end and lateral wing portions E! and 52, respectively, forming, together with the rim portion 53 on the supporting member I2c, cages to receive the springs 5I). In this embodiment of the invention, I replace. the blocker teeth 33 and 34 with radially extending lugs 33a and 34a, respectively, one for each of the thrust members 4Ia. Each lug may have chamfered blocking surfaces 35a engageable with cooperative and inclined blocking surfaces 36a, formed on the adjacent recessed end walls of the clutch element I4a. Relative rotation between the synchronizer-blocker rings and clutch element I4a is limited by the lug engagement with its adjacent blocking surface 36a. The thrust connection between the clutch element and thrust members is by way of frictional engagement only, the same as in the preferred form previously described. The thrust members 4Ia, in this embodiment, may be of relatively rigid construction, the end wings 5I providing thrust engagement with the rear faces 54 of the lugs 33a and 34a, respectively.

I claim:

l1. A transmission -synchronizer comprising a 0 pair lof torque-transmitting mem-bers mounted in axial alignment, a movable jaw clutch element drivingly associated with one of said members and adapted to be moved into engagement with a Jaw clutch element drivingly associated with the other member thus to establish a positive drive connection between said members, a synchronizer element having a lost m-otion drive connection with said one member and adapted to be moved into frictional driving engagement with said other member, and means including thrust members having relatively low inertia relative to said movable jaw clutch element, each operatively interposed between said synchronizer element and said movable clutch element for transmitting thrust fr-om said movable clutch element to said synchronizer element in the dieach comprising a radially outwardly bowed central region in purely frictional engagement with the interior of the movable clutch element and a radially inwardly extending end portion engaging said synchronizer element, whereby to transmit to the latter, from said movable clutch element, suiiioient thrust to initiate frictional driving engagement.

2. A transmission synchronizer comprising a pair of torque-transmitting members mounted in axial alignment, a movable jaw clutch element carried -by one of said members andadapted to be moved into engagement with a jaw clutch elemen-t .carried by the other member thus to establish a positive drive connection between said members, 'a synchronizer element having a klost motion drive connection with said one member and adapted to be moved into frictional driving engagement with said other member, and means including thrust members having relatively low inertia relative to said movable jaw clutch element, each operatively interposed between said synchronizer element and said movable clutch element for transmitting thrust from said movable clutch element to said synchronizer element in the direction of said other torque-transmitting member, thus to establish a frictional driving connection between said pair of torque members, each of said thrust members being maintained in uniform resistance frictional contact with said wmovable clutch element in an amount sufficient to prevent slippage Ibetween said thrust members and said clutch element until frictional driving engagement is initiated between said other torque member and said synchronizer element.

3. A transmission synchronizer comprising a pair of torque-transmitting members mounted in axial alignment, a movable jaw clutch element drivingly associated with one of said members and adapted to be moved into engagement with a jaw clutch element drivingly associated with the other member thus to establish a positive drive `connection between said members, a Synchronizer element adapted to be moved into frictional driving engagement with said other member, and a thrust member operatively interposed between said movable clutch element and said synchronizer element, said movable clutch element engaging said thrust member with a uniform resistance, purely frictional engagement so as to transmit to said synchronizer element, through the medium of said thrust member, suiiicient thrust to initiate frictional driving engagement between said other torque member and said synchronizer element.

4. A transmission synchronizer comprising a pair of torque-transmitting members mounted in axial alignment, a movable jaw clutch element drivingly associated with one of said members and adapted to be moved into engagement with a jaw clutch element drivingly associated with the other member thus to establish a positive drive connection between said members, a synchronizer element adapted to Vbe moved into frictional driving engagement with said other member, and a thrust member operatively interposed between said movable clutch element and said synchronizer elementsaid movable clutch element engaging said thrust member with an engagement which is developed, in al1 positions of shifting movement, between surfaces of said movable clutch element and said thrust member that are parallel to the `axis of shifting movement, whereby to transmit through the medium of said thrust member, to said synchronizer element, suilicient thrust to initiate frictional clutching engagement between the latter and said other torque transmitting member.

5. A transmission synchronizer comprising a pair of torque-transmitting members mounted in axial alignment, a movable jaw clutch element drivingly associated with one of said members an-d adapted to be moved into engagement with a jaw clutch element drivingly associated with the other member thus to establish a positive drive connection between said members, a synchronizer element having a lost motion drive connection with said one member and adapted to be moved into frictional driving engagement with said other member, and a thrust member operatively interposed between said movable clutch element and said synchronizer element and conned under compression by engagement with said movable clutch element, such engagement being developed, `in all positions of shifting movement, between surfaces of said movable clutch element and said thrustmembers that are parallel to the axis of shifting movement, and adapted to transmit to said synchronizer element, through the medium of said thrust member, sufficient thrust to initiate frictional clutching engagement between said other torque member and said synchronizer element.

6. A transmission synchronizer comprising a pair of torque-transmitting members mounted in axial alignment, a movable jaw `clutch element drivingly associated with one of said members and adapted to bemoved into engagement with a jaw clutch element drivingly associated with the other member thus to establish a positive drive connection between said members, a synchronizer element adapted to be moved into frictional driving engagement with said other member, and a thrust member of spring metal operatively interposed between said movable clutch element and said synchronizer member and biased under :compression in uniform resistance, purely frictional engagement with said movable clutch element, whereby to transmit `:from the latter to said synchronizer element, suilicient thrust to initiate frictional clutching engagement.

7. A transmission synchronizer comprising a pair of torque-transmitting members mounted in axial alignment, a. movable jaw Iclutch element drivingly associated with one of said members and adapted to be moved into engagement with a jaw `clutch element drivingly associated with the other member thus to establish a positive drive connection between said members, a synchronizer element having `a lost motion drive connection with said one member and adapted to be moved into lfrictional driving engagement with said other member, and a thrust member of spring metal operatively interposed between said movable clutch element and said synchronizer element and biased .under compression in uniform resistance, purely frictional engagement with said movable clutch element," whereby to transmit from the latter to said synchronizer element, suiiicient thrust to initiate frictional driving engagement.

8. A transmission synchronizer comprising a pair of rtorque-transmitting mem-bers mounted in axial alignment, a movable jaw clutch element drivingly associated with one of said members and adapted to be moved into engagement with ajaw clutch element drivingly associated with the other member thus to establish a positive drive connection between said members, a synchronizer element adapted to be moved into frictional driving engagement with said other member, and a thrust member of spring metal operatively interposed between said movable clutch element and said synchronizer element, said movable clutch element engaging said thrust member through engaging surfaces of said movable clutch element and thrust member respectively that are at all times parallel over their entire engaging areas to the direction of movement of said synchronizer element, and .conning said thrust member under compression so as to produce an engagement that is at all times purely frictional and f such quantity as to transmit to said synchronizer element, through the medium of said thrust member, sufficient thrust to initiate driving engagement between said other torque member and said synchronizer element.

9. A transmission synchronizer comprising a pair of torque-transmitting members mounted in axial alignment, a movable jaw clutch element carried by one of said members and adapted to be moved into engagement with a jaw clutch element carried by the other member thus to establish a positive drive connection between said members, a synchronizer element having a lost motion drive connection with said one member and adapted to be moved into frictional driving engagement with said other member, said movable clutch element having an interior friction surface, and a thrust member of spring metal operatively interposed and biased under compression between said movable clutch element and said synchronizer element, said thrust member including a central arched region having a surface in frictional engagement with said interior friction surface of the movable clutch element, the entire engaging areas of both of said engaging surfaces being parallel to the direction of movement of said synchronizer element, whereby said engagement is, in said direction, a purely frictional one; said engagement being of such quantity as to transmit to said synchronizer element, through the medium of said thrust member, sufficient thrust to initiate driving engagement between said other torque member and said synchronizer element.

10. A transmission synchronizer comprising a pair of torque-transmitting members mounted in axial alignment, a movable jaw clutch element carried by one of said members and adapted to be moved into engagement with a jaw clutch element carried by the other member thus to establish a positive drive connection between said members, a synchronizer element having a lost motion drive connection with said one member and adapted to be moved into frictional driving engagement with said other member, said movable clutch element having an interior friction surface, and a thrust member of spring metal operatively interposed and biased under compression between said movable clutch element and said synchronizer element, said thrust member including end portions engaging said one torque member and adapted to transmit thrust thereto, and a central arched region having a surface in frictional engagement with said interior friction surface of the movable clutch element, the entire engaging areas of both of said engaging surfaces being parallel to the direction of movement of said synchronizer element, whereby said engagement is, in said direction, a purely frictional one; said engagement being of such quantity as to transmit to said synchronizer element, through the medium of said thrust member, suiiicient thrust to initiate driving engagement between said other torque member and said synchronizer element.

11. A transmission synchronizer comprising a pair of torque-transmitting members counted in axial alignment, a movable jaw clutch element carried by one of said members and adapted to be moved into engagement with a jaw clutch element carried by the other member thus to establish a positive drive connection between said members,u a synchronizer element having a lost motion drive connection with said one member and adapted to bev moved into frictional driving engagement with said other member, said movable clutch element having an interior friction surface, a thrust member operatively interposed between said movable clutch element and said synchronizer element, said thrust member having a friction face engageable with said interior friction surface, the entire engaging areas of said face and surface being parallel to the direction of movement of said synchronizer element, whereby said engagement is, in said direction, a purely frictional one, and a coil spring engaged between said thrust member and said clutch supporting member so as to urge said thrust member against said interior friction surface with sufficient force so that the frictional engagement between said face and interior surface will transmit to said synchronizer element, through the medium of said thrust member, sufficient thrust to initiate frictional driving engagement between said other torque member and said synchronizer element.

12. In a synchronizing transmission, a pair of axially aligned torque-transmitting members, an annular movable jaw clutch element surrounding and drivingly connected to one of said members and axially shiftable into engagement with a jaw clutch element drivingly associated with the other member, thus to establish a positive drive connection between said members, a synchronizer element drivingly associated with said one member and adapted to be moved into frictional driving engagement with a friction clutch element drivingly associated with the other member, and a thrust member radially interposed between said movable jaw clutch element and said one torque-transmitting member, axially movable relative to both said movable jaw clutch element and said one member, and having a .purely frictional engagement with an interior surface of said movable clutch element and a positive thrust transmitting engagement with said synchronizer element whereby axial shifting movement of said sleeve will result in the transmission of thrust to said synchronizer element for establishing frictional driving engagement between said synchronizer element and said friction clutch element.

13. A transmission synchronizer as defined in claim 4, wherein said thrust member is in the form of a bar disposed parallel to the axis of said members.

14. A transmission synchronizer as defined in claim 4, wherein said thrust member is in the form of a bar positioned in an axially extending notch in the interior of said movable clutch element.

15. A transmission synchroniser comprising a pair of torque-transmitting members mounted in axial alignment, a movable jaw clutch sleeve drivingly associated with one of said members and axially shiftable into engagement with a jaw clutch element drivingly associated withthe other member thus to establish a positive drive connectionl between saidy "members, 4a,"lsynchroniz'er "element adapted to'be shifted arkially'into frictional driving engagement witha 'cornplementaiy friction clutch element drivingly .associated withsaid other member so as to establish africtional drive 'connection between said` membersga thrust mem- `beroperatively interposed betvrsrfeenfl said sleeve and said synchronizer element and engagingvthe 'interior of said sleeve with an engagement which is developed, in rall positions 4( )t'shifti'ng `movement,'between surfaces ofsaid sleeveand said Athrustmember"that are parallel to the axisof shifting movement,'whereby fto transmit through ythe medim ofy said thrust member to said synchronizerelement ysuilicier'it thriistto initiate frictionaly clutching engagement between the latter and' said friction clutchl element, vand spring lmeans engaged between said thrust member and said one torque-transmitting member so as to urge said thrust member against` the intericrof said sleeve to establish saidthrust transmitting engagement. n I

16. Ina synchronizing mechanism, two relatively rotatable'partseach,havinga set of clutch teeth and a friction clutching member," a'third rotating partadapted for selective drive "relation with the V1lrst"said parts,V a hubstrcture carried by `said third 'part for 'rotetiqnthrewith and fixed against movement axiallythe'reof, ka' shift chroriizingfstructures for "e ecting displacement of said synchronizing "strnctiires'in response to shift of said v'shift device thereby to selectively engage Isaid synchronizing structures with Vsaid friction cltching memberahsaid releasable connecting means accommodating further shift of said shift devicerelative to saidsynchronizing structuresto" selectively engagetlie clutch teeth `thereof withsaid sets of clutch teeth, said releasable connecting 4means comprising a thrust transmitting 'element frictionally engaging said shift Ydevice for selective displacementl therewith in transmitting thrust therefrom to ysaidl synchronizing structures thereby to effect said selec- `tive displacement of the latter.

17.` In a synchronizing mechanism, two relatively rotatable p'arts each having a setof clutch teeth and a friction clutching member, a third lrotating part adapted for selective drive relation with the rst said parts, a hub structure carried by said third part for rotation therewith and fixed against movement axiallyathereof, a shift device having drive connection With said vhub structure and having clutch teeth adapted'for selective clutching with said sets of clutch teeth,

ya'pair of synchronizing structures rotating with said vhub structure and adapted for displacement 'relative to each other and relativeto 'said hb structure to respectively vengage said synchronizing structures with said friction clutching members,A each of said synchronizing structures being adapted to have limited rotative movement relative to said hub structure, and including blocking means adapted as a result of initial engagement with a coacting friction clutching member, to be disposed in a position blocking advance of said shift device while differential rotation exists between the coacting friction clutch surfaces. and means providing a releasable connection between saidshifrt device and said synchronizing structures forrevffe'cting displacement of'said synchronizing structures in response to shift of said shiftdevioe` therebymto selectively engage said synchronizingfstrctures with vsaid friction 'clutching members,`said 'releasable connecting means` accommodating further4 shift of said shift device relative to said synchronizing structures' to Yselectively engage the clutch teeth thereof With said sets of clutch teeth, said rreleasable connecting means comprising a thrust transmitting element frictionally engaging said shift device for vselective displacement rtherewith1in transmitting thrust therefrom to said synchronizingstrnctures thereby to effec'tlsaid selective displacementof thelatter. a

sAMUEL o. WHITE. 

